This project will identify the precursors, correlates, and consequences of social and communicative skills in children wit autism. The first study will specify the characteristics of the home and school environment that are associated with communication and language skills in very young children with autism and are predictive of their gains in these skills over the course of a year. The central hypothesis to be tested is that, while autism is caused by biological determinants, environmental factors contribute to those social communication skills, which crucially determine the later development of children with autism. A more specific hypothesis to be examined is that the optimal development of children with autism requires both responsive caregiving and the provision of structured experiences. The identification of environmental correlates of social communication skills is crucial for the planning of interventions. The second study continues the longitudinal follow-up of a sample of 51 children with autism who were tested at 3-5 years of age as well as one and eight years later. The objectives of this follow-up are to chart the course of the disorder into the period of late adolescence and early adulthood and determine the consequences of earlier individual differences for later communicative, social, and adaptive abilities.